1. Field of the Invention
This invention relates to a printing apparatus, a printing method and program, for printing, by use of plural kinds of inks, image onto a printing medium, in plural printing modes including at least a double-sided printing mode in which images are printed on both sides of the printing medium, the plural number of kinds of inks including at least one kind of pigmented ink and at least one kind of dye ink.
2. Description of the Related Art
Conventionally, printing apparatuses configured as printers or copying machines are constructed to print image on a printing material (hereafter called “printing medium”) in response to printing information. These printing apparatuses can be classified in accordance with their respective printing methods, such as inkjet printing, wire dot printing, thermal transfer imaging, and laser beam printing. Printing apparatus by using inkjet printing method (hereafter called “inkjet printing apparatus”) print image by ejecting ink droplets from a printing means (hereafter called “printing head”) onto the printing medium, and have advantages such as an ease of making the printing apparatus compact, a capability of high resolution image in high speed printing, a lower running cost, a lower noise due to being non-impact printing, and an ease of color image printing by using a large number of color inks.
Inks used for such inkjet printing apparatuses have conventionally been dye inks, which are produced by various water-soluble dyes dissolved in either water or a mixture of water and organic solvents. However, images printed by dye inks are somewhat inferior in image fastness such as light-fastness.
There has now come to be used pigmented ink, which is produced by dissolving the pigment dispersion liquid wherein a pigment is dispersed in a polymer dispersant. The characteristic of the pigmented ink is superior to the dye ink in image fastness such as water fastness. Since pigments have larger particle size of coloring agent than that of dyes, they are difficult to penetrate into the fibers of the printing medium such as plain paper, and stay near the surface thereof. As a result, the printing density increases, and the penetration to surrounding area becomes less, thus the boundaries of image are clearly printed. Currently, however, since pigmented inks other than black are somewhat inferior to the dye inks in terms of coloring ability many of ink jet printing apparatuses apply pigmented ink only for black ink, and apply dye inks for color inks such as cyan, magenta, and yellow.
In the meantime, in recent years there have increasingly become popular the ecological movements, and as a part of which, in view of preserving paper resources, printing on both sides of a printing medium (double-sided printing mode) is required of printing apparatuses.
Published references for such double-sided printing mode are available. For example, Japanese Patent Application Laid-open No. 7-314734 (1995) in which disclosed is a countermeasure to suppress a see-through of the image printed on back side of a printing medium in the double-sided printing mode in which printing is effected to both sides of the printing medium. More specifically, a printing in a lower printing density in the double-sided printing mode than in the single-sided printing mode is disclosed therein.
Incidentally, since the pigmented inks are fixed near the surface of the printing medium, a see-through does not occur so much, if a double-sided printing is done. However, because the pigmented ink is inferior to the dye ink in abrasion resistance, the pigmented ink is subject to rubbing of in the double-sided printing mode. Specifically because, in the double-sided printing mode, the printing medium is turned over after being printed on the front side thereof and transported with the printed side while being kept in contact with the transport route, the pigmented ink on the printed surface tend to be rubbed off. Therefore, a countermeasure is required to restrain such rubbed off of the pigmented ink for the double-sided printing mode using the pigmented ink.
However, the aforementioned Japanese Patent Application Laid-open No. 7-314734 (1995) discloses neither a double-sided printing mode by using the pigmented inks, nor a method to limit an abrasion of the pigmented inks in the double-sided printing mode. Furthermore, Japanese Patent Application Laid-open No. 7-314734 (1995) does not disclose a printing feature by using both the pigmented ink and the dye ink, nor does it disclose specifically a preferable double-sided printing mode using both the pigmented ink and the dye ink. Consequently, it does not disclose any method to restrain a rubbing off of the pigmented ink in a double-sided printing mode using both the pigmented ink and the dye ink.